Spring Boot 2.7.5中Log4j2脚本支持未启用的替代方案咨询

针对你遇到的Log4j2 Groovy脚本默认禁用、需批量修改项目的问题，以下几种方案可在共享日志库内实现解决，无需改动各业务项目：

方案1：利用Log4j2初始化钩子自动启用Groovy #

Log4j2支持自定义初始化类，可在共享库中实现自动设置系统属性：

1. 创建初始化类
   在共享日志库中编写实现PluginInitializer的类：

package com.your.shared.log.library;

import org.apache.logging.log4j.core.config.plugins.util.PluginInitializer;

public class Log4j2GroovyEnabler implements PluginInitializer {
    @Override
    public void initialize() {
        // 仅在未设置属性时覆盖，保留外部配置优先级
        if (System.getProperty("log4j2.Script.enableLanguages") == null) {
            System.setProperty("log4j2.Script.enableLanguages", "groovy");
        }
    }
}

2. 注册初始化类
   在共享库的src/main/resources/META-INF/services目录下创建文件org.apache.logging.log4j.core.config.plugins.util.PluginInitializer，内容为初始化类的全限定名：

com.your.shared.log.library.Log4j2GroovyEnabler

Log4j2启动时会自动加载该类并执行初始化逻辑，无需业务项目做任何修改。

方案2：Spring Boot自动配置前置设置属性 #

如果共享库是Spring Boot依赖，可通过自动配置类在容器启动前设置属性：

1. 编写自动配置类

package com.your.shared.log.library.autoconfigure;

import org.springframework.context.annotation.Configuration;
import javax.annotation.PostConstruct;

@Configuration
public class Log4j2GroovyAutoConfig {

    @PostConstruct
    public void enableGroovyScripting() {
        if (System.getProperty("log4j2.Script.enableLanguages") == null) {
            System.setProperty("log4j2.Script.enableLanguages", "groovy");
        }
    }
}

2. 注册自动配置
   在共享库的src/main/resources/META-INF/spring/org.springframework.boot.autoconfigure.AutoConfiguration.imports文件中添加配置类全限定名：

com.your.shared.log.library.autoconfigure.Log4j2GroovyAutoConfig

Spring Boot启动时会优先加载该配置，确保属性在Log4j2初始化前生效。

方案3：替换Groovy脚本为自定义AppenderSelector插件（推荐） #

彻底摆脱对脚本的依赖，用Java实现原Groovy脚本的逻辑，更稳定可控：

1. 编写自定义AppenderSelector

package com.your.shared.log.library;

import org.apache.logging.log4j.core.Appender;
import org.apache.logging.log4j.core.LogEvent;
import org.apache.logging.log4j.core.config.AppenderControl;
import org.apache.logging.log4j.core.config.Configuration;
import org.apache.logging.log4j.core.config.plugins.Plugin;
import org.apache.logging.log4j.core.config.plugins.PluginConfiguration;
import org.apache.logging.log4j.core.config.plugins.PluginElement;
import org.apache.logging.log4j.core.config.plugins.PluginFactory;
import org.apache.logging.log4j.core.config.plugins.validation.constraints.Required;

import java.util.HashMap;
import java.util.Map;

@Plugin(
        name = "GraylogAppenderSelector",
        category = Configuration.CATEGORY,
        elementType = AppenderSelector.ELEMENT_TYPE,
        printObject = true
)
public class GraylogAppenderSelector implements AppenderSelector {

    private final Map<String, AppenderControl> appenderMap;

    private GraylogAppenderSelector(Map<String, AppenderControl> appenderMap) {
        this.appenderMap = appenderMap;
    }

    @PluginFactory
    public static GraylogAppenderSelector createSelector(
            @PluginConfiguration Configuration config,
            @PluginElement("Appenders") @Required Appender[] appenders) {
        Map<String, AppenderControl> map = new HashMap<>();
        for (Appender appender : appenders) {
            map.put(appender.getName(), config.getAppenderControl(appender));
        }
        return new GraylogAppenderSelector(map);
    }

    @Override
    public AppenderControl[] getAppendersForEvent(LogEvent event) {
        // 实现原Groovy脚本中的选择逻辑，比如根据MDC字段、日志级别选择对应Graylog Appender
        String targetAppender = event.getContextData().getValue("graylogTarget");
        if (targetAppender != null && appenderMap.containsKey(targetAppender)) {
            return new AppenderControl[]{appenderMap.get(targetAppender)};
        }
        // 默认返回主Appender
        return new AppenderControl[]{appenderMap.get("DefaultGraylogAppender")};
    }
}

2. 修改log4j2.xml配置
   替换原ScriptAppenderSelector为自定义插件：

<Appenders>
    <Gelf name="DefaultGraylogAppender" server="graylog-primary" port="12201" />
    <Gelf name="GraylogBackupAppender" server="graylog-backup" port="12201" />
    
    <GraylogAppenderSelector name="GraylogSelector">
        <AppenderRef ref="DefaultGraylogAppender"/>
        <AppenderRef ref="GraylogBackupAppender"/>
    </GraylogAppenderSelector>
</Appenders>

此方案完全规避了脚本禁用限制，逻辑更易维护，性能也更优。

内容的提问来源于stack exchange，提问作者MAvim